High Voltage Semiconductor Power Switching Device

ABSTRACT

A three terminal high voltage Darlington bipolar transistor power switching device includes two high voltage bipolar transistors, with collectors connected together serving as the collector terminal. The base of the first high voltage bipolar transistor serves as the base terminal. The emitter of the first high voltage bipolar transistor connects to the base of the second high voltage bipolar transistor (inner base), and the emitter of the second high voltage bipolar transistor serves as the emitter terminal. A diode has its anode connected to the inner base (emitter of the first high voltage bipolar transistor, or base of the second high voltage bipolar transistor), and its cathode connected to the base terminal. Similarly, a three terminal hybrid MOSFET/bipolar high voltage switching device can be formed by replacing the first high voltage bipolar transistor of the previous switching device by a high voltage MOSFET.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/064,843 filed on Oct. 28, 2013.

BACKGROUND OF THE INVENTION

The present invention relates to high voltage semiconductor switchingdevices. The invention more particularly, although not exclusively,relates to switching device for switching converter applications.

Prior art switching converter circuits are shown in FIGS. 1 and 2. FIG.1 shows an isolated constant voltage output switching converter whileFIG. 2 shows a non-isolated switching converter having constant currentoutput for driving LED lighting.

In both FIGS. 1 and 2, the selection of the power switching device (115and 215 respectively) is a key decision. Bipolar transistor and MOSFETare typical candidates for power switching device. Bipolar transistorsare much less costly than the MOSFET at the same power rating. However,MOSFETs are normally more preferred, especially at high power levels,due to the following reasons:

-   -   a. Bipolar transistors require continuous base current to keep        them in the turn on state while MOSFETs only require the charge        up of the gate capacitance to turn them on;    -   b. The current gain for power bipolar transistors with high        breakdown voltage (say, 600V or more) is usually not high (say,        at around 10 to 20, or even less than 10). This renders the        power for driving the base substantial, especially when the        power converter delivers high power to its output. The        efficiency of the switching converter circuit will then be        degraded.

By using bipolar transistors in a Darlington configuration, effectivecurrent gain becomes product of individual transistor current gain.Hence, effective current gain of a few hundred can be obtained easilyand the power loss due to base driving can be reduced to comparable withthe gate driving for MOSFET counterpart at the same power level.However, commercially available Darlington transistors are normallybeing offered in three pin package in which B is the first base and E isthe last emitter as shown in FIG. 3. It is easy to turn on by a smallbase current but the turn off is very slow due to base relaxation at theinner base (base pin for transistors 302 and 304 in FIG. 3). Therefore,it is not suitable for switching converter application as slow switchingtransition generates substantial amount of heat at the switching device,as well as degradation of efficiency.

IGBT is a hybrid power switching device that attempts to combine theadvantage of MOSFET and bipolar transistor. For IGBT, the power for thegate driving is small as it is the charge up of the control gatecapacitance similar to the case of MOSFET while the chip size is similarto bipolar transistor for the same rated current due to the conductionmode is bipolar action. However, due to the actual bipolar base terminalis inside the device, it suffers the same problem of slow switching offas the three terminal Darlington bipolar transistor.

As of today, MOSFET is still the most widely used choice for powerswitching device.

SUMMARY

A high voltage three pin Darlington bipolar power switching device withfast turn off time is provided.

A high voltage hybrid MOSFET/bipolar power switching device with fastturn off time is also provided.

Each of these power switching devices can be fabricated as monolithicdevices.

There is disclosed herein a three terminal high voltage Darlingtonbipolar transistor power switching device including the followingcomponents:

two high voltage bipolar transistors, with collectors connected togetherserving as the collector terminal for the power switching device, thebase of the first high voltage bipolar transistor serving as the baseterminal of the power switching device, the emitter of the first highvoltage bipolar transistor connecting to the base of the second highvoltage bipolar transistor (inner base), and the emitter of the secondhigh voltage bipolar transistor serving as the emitter terminal of thepower switching device; and

a diode with its anode connected to the inner base (emitter of the firsthigh voltage bipolar transistor, or base of the second high voltagebipolar transistor), and its cathode connected to the base terminal ofthe power switching device.

Preferably, the diode is a Schottky diode.

Alternatively, the diode can take the form of a diode connector bipolartransistor.

Preferably, all components are integrated as a monolithic IC using highvoltage SOI process.

Preferably, all components are integrated as a monolithic IC usingmodified high voltage planer process.

There is further disclosed herein a method of fabricating a threeterminal high voltage Darlington bipolar power switching including thesteps of:

conductive die attaching two high voltage bipolar transistors having thesubstrate as collector terminal to the main die pad of a three pin powerdevice package, which serves as the collector terminal for the powerswitching device;

conductive die attaching a diode with cathode as substrate to the basebonding pin of the base terminal of the three pin power device package;

bonding the base of the first high voltage bipolar transistor to thebase terminal of the three pin power device package;

inter-chip bonding of the emitter of the first high voltage bipolartransistor to the base of the second high voltage bipolar transistor;

bonding of the emitter of the first high voltage bipolar transistorand/or the base of the second high voltage bipolar transistor to theanode of the diode;

bonding of the emitter of the second high voltage bipolar transistor tothe emitter pin of the three pin power package; and

subsequent standard moulding and follow on process to complete thedevice packaging.

The diode can be a Schottky diode.

There is further disclosed herein a method of fabricating a threeterminal high voltage Darlington bipolar power switching deviceincluding the steps of:

conductive die attaching a single semiconductor chip high voltageDarlington bipolar transistor having four terminals—namely collector,first base, inner base, and emitter, with the substrate as the collectorterminal, to the main die pad of a three pin power device package, whichis also electrically connected to the collector terminal of the package;

conductive die attaching a diode with cathode as substrate to the basebonding pin of the base terminal of the three pin power device package;

bonding the first base of the high voltage Darlington bipolar transistorto the base terminal of the three pin power device package;

bonding the inner base of the high voltage Darlington bipolar transistorto the anode of the diode;

bonding the emitter of the high voltage Darlington bipolar transistor tothe emitter pin of the three pin power package; and

subsequent standard moulding and follow on process to complete thedevice packaging.

Again, the diode can be a Schottky diode.

There is further disclosed herein a monolithic three terminal highvoltage Darlington bipolar power switching semiconductor integratedcircuit including:

two high voltage bipolar transistors, with their substrates as a commoncollector and also serving as the collector terminal of the powerswitching integrated circuit at the back side;

two semiconductor well regions with the opposite dopant type to thesubstrate serving as the base regions for the high voltage bipolartransistors;

high doping density semiconductor electrodes of the same type as thesubstrate inside the base regions serving as emitters for the highvoltage bipolar transistors; wherein:

the base of the first high voltage bipolar transistor serves as the baseterminal of the power switching integrated circuit;

the emitter of the first high voltage bipolar transistor connects to thebase of second high voltage bipolar transistor (inner base);

the emitter of the second high voltage bipolar transistor serves as theemitter terminal of the power switching integrated circuit; and

a diode with its anode connected to the inner base and its cathodeconnected to the base terminal of the power switching integratedcircuit; wherein

the diode is a diode connected bipolar transistor with the following:

its collector as a well with opposite dopant type to the substrate onthe substrate of the high voltage bipolar transistors;

a base inside the collector well with dopant type different from that ofthe collector well and interconnected to other components viaelectrodes;

an emitter, either as a semiconductor of the same type as the collector(for a normal diode), or as barrier metal silicide (for a Schottkydiode); and

the base and collector terminals being mutually connected and serving asthe cathode while the emitter serves as the anode of the diode.

Preferably, the collector well for the diode connected bipolar sharesthe same mask for fabricating the wells for the base regions of the twohigh voltage bipolar transistors, or is a separate region fabricated byadditional masking.

Preferably, the collector well of for the diode connected bipolar hashigh doping density regions guarding a low doping density region of thesame type with a junction depth less than the high doping region, thehigh doping regions being used for withstanding the high breakdownvoltage as well as connecting the low doping density collector well formaking connection to other electrodes. The low doping density region isserving as the actual collector well inside which the base and emitterof the diode connected bipolar device are formed.

Preferably, the well for the collector of the diode connected bipolartransistor device is merged with the base of the first high voltagebipolar transistor (base pin of the three terminal high voltageDarlington bipolar power switching integrated circuit).

Preferably, connections to the base regions of the high voltage bipolartransistors forming the Darlington device and the collector region ofthe diode connected bipolar device using a normal base emitter junctionare made via the same kind of semiconductor electrode for the anode ofthe diode.

Alternatively, the integrated circuit is monolithic and the diodeconnected bipolar has a Schottky base emitter junction and connectionsto the Schottky diode anode make direct contact thereto.

Preferably, connections to other semiconductor regions are made viabarrier metal silicide for a monolithic power switching integratedcircuit with a Schottky diode in the form of diode connected bipolardevice.

There is further disclosed herein a three terminal high voltage hybridMOSFET/bipolar transistor power switching device including thefollowing:

a high voltage MOSFET and a high voltage bipolar transistor, with thechannel terminals of the MOSFET connected to the collector and baseterminals of the bipolar transistor respectively, the collector andemitter of the bipolar transistor serving as the collector and emitterterminals of the power switching device respectively, and the gate ofthe MOSFET serving as the gate terminal of the three terminal highvoltage hybrid MOSFET/bipolar transistor power switching device; and

a diode with the anode connected to the base of the high voltage bipolartransistor, and the cathode connected to the gate terminal of the powerswitching device.

The diode can be a Schottky diode.

The diode can (less preferably) take the form of a diode connectorbipolar transistor.

Preferably, all components are fabricated on a monolithic IC using ahigh voltage SOI process.

Preferably, all components are fabricated as a monolithic IC using aplaner, super-junction, or semi-super-junction high voltage process.

There is further disclosed herein a method of fabricating a threeterminal high voltage hybrid MOSFET/bipolar power switching device,including the steps of:

conductive die attaching a high voltage MOSFET and a high voltagebipolar transistor having the substrate as drain and collector terminalrespectively, to the main die pad of a three pin power device package,which serves as the collector terminal for the power switching device;

conductive die attaching a diode with cathode as substrate to the gatebonding pin of the gate terminal of the three pin power device package;

bonding the gate of the high voltage MOSFET to the gate terminal of thethree pin power device package;

inter-chip bonding of the source of the high voltage MOSFET to the baseof the high voltage bipolar transistor;

bonding of the source of the high voltage MOSFET and/or the base of thehigh voltage bipolar transistor to the anode of the diode;

bonding of the emitter of the high voltage bipolar transistor to theemitter pin of the three pin power package; and subsequent standardmoulding and follow on process to complete the device packaging.

The diode can be a Schottky diode.

There is further disclosed herein a monolithic three terminal highvoltage hybrid bipolar MOSFET/bipolar power switching semiconductorintegrated circuit fabricated by high voltage planer process including:

a high voltage MOSFET and a high voltage bipolar transistor, withsubstrate as the drain and collector respectively such that thesubstrate serves as the collector terminal for the switching integratedcircuit via high doping concentration region of the same type at theback side;

two semiconductor well regions with the opposite dopant type to thesubstrate serving as the body and base regions for the high voltageMOSFET and high voltage bipolar transistor respectively;

semiconductor electrodes of the same dopant type as the substrate withhigh doping density inside the body and base regions serving as sourceand emitter for the high voltage MOSFET and high voltage bipolartransistors respectively;

poly-silicon thin oxide gate electrodes overlapping the body and thesubstrate regions serving as the gate for the MOSFET; wherein:

the gate of the high voltage MOSFET serves as the gate terminal for thepower switching integrated circuit;

the source terminal of the high voltage MOSFET connecting to the base ofthe high voltage bipolar transistor;

the body of the high voltage MOSFET connecting either to the source ofthe high voltage MOSFET, or as an alternative, to the emitter of thehigh voltage bipolar transistor;

the emitter of the high voltage bipolar transistor serving as theemitter terminal for the power switching integrated circuit; and

a diode with the anode connected to the base of the high voltage bipolartransistor and the cathode connected to the gate terminal of the powerswitching integrated circuit; wherein:

the diode is a diode connected bipolar transistor with the following:

the collector with dopant type opposite to the main substrate as a wellon the substrate of the high voltage bipolar transistor similar to thebody of the high voltage MOSFET, or the base of the high voltage bipolartransistor;

a base inside the collector well with dopant type opposite from that ofthe collector well with interconnections to other parts via electrodesimilar to the emitter regions of the high voltage bipolar transistor,or the source of the high voltage MOSFET;

an emitter, either as semiconductor of the same type as the collector atmuch higher doping density (for a normal diode), or as barrier metalsilicide (for Schottky diode); and

the base and collector terminal are connected and serve as the cathodewhile the emitter serves as the anode of the diode.

Preferably, the collector well of for the diode connected bipolar sharesthe same mask for fabricating the wells for the body and base regions ofthe high voltage MOSFET and high voltage bipolar transistor, or as aseparate region fabricated by additional masking.

Preferably, the collector well of for the diode connected bipolar hashigh doping density regions guarding a low doping density region of thesame type with a junction depth less than the high doping region. Thehigh doping regions are used for withstanding the high breakdown voltageas well as connecting the low doping density collector well for makingconnection, the low doping density region serving as the actualcollector well inside which the base and emitter of the diode connectedbipolar device are formed.

Preferably, the wells for the body of the high voltage MOSFET and thebase of the high voltage bipolar transistor are merged for the case inwhich the body of the MOSFET is electrically connected to the base ofthe high voltage bipolar transistor.

Preferably, the diode is a Schottky diode and connections tosemiconductor regions other than the Schottky diode anode are made viabarrier metal silicide.

Preferably, connections to base region of the high voltage bipolartransistor and the body region of the high voltage MOSFET, and thecollector region of the diode connected bipolar device using a normalbase emitter junction are made via the same kind of semiconductorelectrode for the anode of the diode.

There is further disclosed herein a monolithic three terminal highvoltage hybrid bipolar MOSFET/bipolar power switching semiconductorintegrated circuit fabricated by high voltage super-junction processincluding:

a high voltage MOSFET and a high voltage bipolar transistor, withsubstrate as the drain and collector respectively such that thesubstrate serves as the collector terminal for the power switchingintegrated circuit via high doping density region of the same type atthe back side;

semiconductor well regions with the opposite dopant type to thesubstrate serving as the body and base regions for the high voltageMOSFET and high voltage bipolar transistor respectively, with highdoping concentration super-junction columns of opposite type of dopantas the main substrate for withstanding the high breakdown voltage;

semiconductor electrodes of the same dopant type as the substrate withhigh doping density inside the body and base regions serving as sourceand emitter for the high voltage MOSFET and the high voltage bipolartransistor, respectively;

poly-silicon thin oxide gate electrodes overlapping the body and thesubstrate regions serving as the gate for the MOSFET; wherein:

the gate of the high voltage MOSFET serves as the gate terminal for thepower switching integrated circuit;

the source terminal of the high voltage MOSFET connecting to the base ofthe high voltage bipolar transistor;

the body of the high voltage MOSFET connects to the source of the highvoltage MOSFET, or as an alternative, to the emitter of the high voltagebipolar transistor;

the emitter of the high voltage bipolar transistor serves as the emitterterminal for the switching integrated circuit; and

a diode with the anode connected to the base of the high voltage bipolartransistor and the cathode connected to the gate terminal of the powerswitching integrated device; wherein

the diode is a diode connected bipolar transistor with the following:

the collector with dopant type opposite to the main substrate as a wellon the substrate of the high voltage bipolar transistor similar to thebody of the high voltage MOSFET, or the base of the high voltage bipolartransistor, with high doping concentration super-junction columns ofopposite type of dopant of the substrate guarding the collector regionfor withstanding the high breakdown voltage;

a base inside the collector well with dopant type opposite from that ofthe collector well with interconnections to other parts via electrodesimilar to the emitter regions of the high voltage bipolar transistor,or the source of the high voltage MOSFET;

an emitter, either as semiconductor of the same type as the collector atmuch higher doping density (for a normal diode), or as a barrier metalsilicide (for a Schottky diode); and

the base and collector terminal are connected and serves as the cathodewhile the emitter serves as the anode of the diode.

Preferably, the collector well for the diode connected bipolar sharesthe same mask for fabricating the wells for the body and base regions ofthe high voltage MOSFET and high voltage bipolar transistor, or as aseparate region fabricated by additional masking.

Preferably, the collector well for the diode connected bipolar has highdoping density regions guarding a low doping density region of the sametype with a junction depth less than the high doping region. The highdoping regions are used for withstanding the high breakdown voltage aswell as connecting the low doping density collector well for makingconnection. The low doping density region is serving as the actualcollector well inside which the base and emitter of the diode connectedbipolar device are formed.

Preferably, the wells for the body of the high voltage MOSFET and thebase of the high voltage bipolar transistor are merged for the case inwhich the body of the high voltage MOSFET is electrically connected tothe base of the high voltage bipolar transistor. In addition, isolationregion super-junction columns between the high voltage MOSFET and thehigh voltage bipolar transistor can also be merged, with the isolationregion eliminated.

The diode can be a Schottky diode and connections to semiconductorregions other than the Schottky diode anode are made via barrier metalsilicide.

Preferably, connections to base region of the high voltage bipolartransistor and the body region of the high voltage MOSFET, and thecollector region of the diode connected bipolar device using normal baseemitter junction are made via the same kind of semiconductor electrodefor the anode of the diode.

There is further disclosed herein a monolithic three terminal highvoltage hybrid bipolar MOSFET/bipolar power switching semiconductorintegrated circuit fabricated by high voltage semi-super-junctionprocess comprising:

a high voltage MOSFET and a high voltage bipolar transistor, withsubstrate as the drain and collector respectively such that thesubstrate serves as the collector terminal for the power switchingintegrated circuit via high doping density region of the same type atthe back side;

semiconductor well regions with the opposite dopant type to thesubstrate serving as the body and base regions for the high voltageMOSFET and high voltage bipolar transistor respectively, with highdoping concentration semi-super-junction columns of opposite type ofdopant as the main substrate for withstanding the high breakdownvoltage;

semiconductor electrodes of the same dopant type as the substrate withhigh doping density inside the body and base regions serving as sourceand emitter for the high voltage MOSFET and the high voltage bipolartransistor, respectively;

poly-silicon thin oxide gate electrodes overlapping the body and thesubstrate regions serving as the gate for the MOSFET; wherein:

the gate of the high voltage MOSFET serves as the gate terminal for thepower switching integrated circuit;

the source terminal of the high voltage MOSFET connecting to the base ofthe high voltage bipolar transistor;

the body of the high voltage MOSFET connects to the source of the highvoltage MOSFET, or as an alternative, to the emitter of the high voltagebipolar transistor;

the emitter of the high voltage bipolar transistor serving as theemitter terminal for the power switching integrated circuit; and

a diode with the anode connected to the base of the high voltage bipolartransistor and the cathode connected to the gate terminal of the powerswitching integrated circuit; wherein

the diode is a diode connected bipolar transistor with the following:

the collector with dopant type opposite to the main substrate as a wellon the substrate of the high voltage bipolar transistor similar to thebody of the high voltage MOSFET, or the base of the high voltage bipolartransistor, with high doping concentration semi-super-junction columnsof opposite type of dopant of the substrate guarding the collectorregion for withstanding the high breakdown voltage;

a base inside the collector well with dopant type opposite from that ofthe collector well with interconnections to other parts via electrodesimilar to the emitter regions of the high voltage bipolar transistor,or the source of the high voltage MOSFET;

an emitter, either as semiconductor of the same type as the collector atmuch higher doping density (for normal diode), or as barrier metalsilicide (for Schottky diode); and

the base and collector terminal are connected and serving as the cathodewhile the emitter is serving as the anode of the diode.

Preferably, the collector well of for the diode connected bipolar sharesthe same mask for fabricating the wells for the body and base regions ofthe high voltage MOSFET and high voltage bipolar transistor, or as aseparate region fabricated by additional masking.

Preferably, the collector well of for the diode connected bipolar hashigh doping density regions guarding a low doping density region of thesame type with a junction depth less than the high doping region. Thehigh doping regions are used for withstanding the high breakdown voltageas well as connecting the low doping density collector well for makingconnection. The low doping density region serves as the actual collectorwell inside which the base and emitter of the diode connected bipolardevice are formed.

Preferably, the wells for the body of the high voltage MOSFET and thebase of the high voltage bipolar transistor are merged for the case inwhich the body of the high voltage MOSFET is electrically connected tothe base of the high voltage bipolar transistor. In addition,semi-super-junction columns between the high voltage MOSFET and the highvoltage bipolar transistor can also be merged, with the isolation regionbetween them eliminated.

Preferably, the diode is a Schottky diode and connections tosemiconductor regions other than the Schottky diode anode are made viabarrier metal silicide.

Preferably, connections to the base region of the high voltage bipolartransistor and the body region of the high voltage MOSFET, and thecollector region of the diode connected bipolar device using normal baseemitter junction are made via the same kind of semiconductor electrodefor the anode of the diode.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the present invention will now be described by way ofexample with reference to the accompanying drawings, wherein:

FIG. 1 shows a typical prior art switching converter with isolatedconstant voltage output;

FIG. 2 shows a typical prior art switching converter with non-isolatedconstant current output for LED lighting application;

FIG. 3 illustrates two typical prior art circuit schematic forDarlington transistor with three pin package;

FIG. 4 is a schematic circuit diagram for the invented three pin highvoltage Darlington bipolar power switching device with fast turn offtime;

FIG. 5 illustrates a possible bonding diagram to integrate discretedevices forming the invented high voltage Darlington bipolar powerswitching device into a single three pin package;

FIG. 6 illustrates another possible bonding diagram to integratediscrete devices forming the invented high voltage Darlington bipolarpower switching device into a single three pin package;

FIG. 7 illustrates a possible cross section of the invented high voltageDarlington bipolar switching device as a monolithic IC;

FIG. 8 illustrates another possible cross section of the invented highvoltage Darlington bipolar switching device as a monolithic IC;

FIG. 9 illustrates a third possible cross section of the invented highvoltage Darlington bipolar switching device as a monolithic IC;

FIG. 10 illustrates another possible cross section for the structure ofthe diode connected bipolar device up to the forming of the base region;

FIG. 11 is a schematic circuit diagram for the invented three pin highvoltage hybrid MOSFET/bipolar power switching device with fast turn offtime;

FIG. 12 illustrates a possible bonding diagram to integrate discretedevices forming the invented high voltage hybrid/bipolar power switchingdevice into a single three pin package;

FIG. 13 illustrates a possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage planer VDMOS process;

FIG. 14 illustrates another possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage planer VDMOS process;

FIG. 15 illustrates a third possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage planer VDMOS process;

FIG. 16 illustrates a possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage super-junction VDMOS process;

FIG. 17 illustrates another possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage super-junction VDMOS process;

FIG. 18 illustrates a possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage semi-super-junction VDMOS process;

FIG. 19 illustrates another possible cross section of the invented highvoltage hybrid MOSFET/bipolar switching device as a monolithic IC usingmodified high voltage semi-super-junction VDMOS process;

DETAILED DESCRIPTION

FIG. 4 is a schematic circuit diagram for an embodiment of the inventedthree pin high voltage Darlington bipolar power switching device withfast turn off time. High voltage bipolar transistors 401 and 402 form aconventional Darlington bipolar transistor. The current gain of theDarlington transistor is the product of the individual current gain oftransistor 401 and transistor 402. Typical current gain of 100 to 400can be achieved. Therefore, base current to turn on the Darlingtontransistor is small and the associated power is comparable to the gatedrive for power MOSFET power switching device for handling the sameoutput power level. The addition of the diode 403 is to provide adischarging path for the base of transistor 402 during switch off of theDarlington transistor. Hence, diode 403 ensures fast base relaxation andthus fast turn off of this invented power switching device. For diode403, Schottky diode is more preferred due to the low forward voltage ascompared with the forward voltage of the base emitter junction oftransistor 402. This enables the direct connecting of the emitterterminal of the switching device to Vss. A normal diode can still workdue to the emitter voltage in typical applications is higher than theVss voltage as in the cases of FIG. 1 and FIG. 2. Hence, this inventedpower switching device can be used with the collector and emitterterminals as the positive and negative sides of the power switchingdevice while the base terminal as the control terminal in FIG. 1 andFIG. 2.

The three discrete semiconductor chips forming the invented high voltageDarlington bipolar power switching devices can be packaged into a singlethree pin IC. Bipolar transistors used are having the backside substrateas the collector terminal while the base and emitter terminals are atthe front side with bonding pads. Diode having cathode as substrate andanode pad at front side is used. The two bipolar transistors are dieattached to the main die pad using conductive die attach epoxy. The maindie pad and the collector pin of the package are electrically connected.The diode is conductive die attached to the base pin. Appropriatebonding connects the three individual discrete semiconductor chips intothe circuit as shown in FIG. 4. Further steps such as plastic moulding,etc., to complete the packaging are then carried out to complete thethree pin packaging. FIG. 5 is a bonding diagram for inter-connectingthe discrete devices into a single three pin package.

It should be noted that if high voltage Darlington bipolar transistorchip with four bonding pads, namely collector, emitter, first and innerbase pads, are available, the two bipolar chips in FIG. 5 can be reducedto a single chip and the inter-chip bonding wire between the firstemitter and the second base can be eliminated. The new bonding diagramfor this particular embodiment is illustrated in FIG. 6.

The three discrete devices forming the invented high voltage Darlingtonbipolar power switching device can be fabricated as a monolithicintegrated circuit (IC). Use of high voltage SOI process is an obviousembodiment. Other possible embodiments are discussed in subsequentparagraphs.

The major difficulty in integrating the three discrete devices formingthe invented high voltage Darlington power switching device into amonolithic IC using high voltage planer process is the isolation of thediode from the substrate. A simple diode using a base well as anode andthe emitter electrode inside the base well as cathode will not work dueto the turn on of the parasitic vertical bipolar transistor having thesubstrate acting as the collector in the same way as for the transistorsforming the high voltage Darlington transistor. A diode connectedbipolar is used to provide means to avoid the turn on of the parasitictransistor in the diode region.

FIG. 7 is a cross section of a possible embodiment of such an integratedcircuit. In FIG. 7, N+ region 701 at the back side is used forconductive die attach to the die pad which is also electrically servingas the collector pin, the N− region 702 is the actual collector regionthat can withstand high breakdown voltage. P well 703 is the collectorof a diode connected PNP transistor (725) inside which the N+ regions707 serves as the base, while the P+ region 708 is the emitter. Theemitter 708 serves as the anode while base formed by N+ region 707together with P well collector 703 serve as the cathode of the diodeconnected PNP transistor 725. The use of diode connected PNP transistorinstead of a simple diode using the P well 703 as anode and N+707 ascathode is required due to the vertical NPN transistor 726 formed by N−region 702 as collector, P well region 703 as base, and N+ regions 707as the emitter region, will become on during the time when current flowsfrom the P well anode 703 to the N+ cathode 707. This diode connectedPNP transistor structure ensures that the vertical NPN transistor 726will never be on due to the P well 703 serving as base is always at thesame potential as the N+ emitter region 707 inside it. Furthermore,transistor current gain makes this device smaller as compared withsimple diode for handling the same forward diode current. The P wellregion of this diode connected device 725 may share the same masking,having the same dosage and drive in conditions as other P wells (704 and705) serving as base regions for the 2 bipolar transistors forming theDarlington transistor, or may have another independent P well havinganother masking step, dosage and drive in conditions provided that itcan together with the collector N− layer 702 to withstand the requiredhigh reverse breakdown voltage. P wells 704 and 705 are the base regionsfor the first and inner bipolar transistors (727 and 728) forming theDarlington transistor respectively. N+ regions 711 and 713 are theemitters for the first bipolar transistor for the Darlington transistorwhile N+ regions 716, 718, 721, and 723 are the emitters for the innerbipolar transistor of the Darlington transistor. All such N+ emittersmay and prefer to share the same masking, and have the same dosage asthe N+ region 707 (cathode of the diode connected PNP describedpreviously). The dopant density of P wells 703, 704 and 705 are usuallyhigh enough for making direct ohmic contact with metal. Since an extramasking step is required for making the P+ junction 708, this providesan option to share the same mask to make P+ contacts for metal layer toconnect to these three P well regions. Since P well 703 and P well 704are at the same potential (electrically connected), it is preferred tomerge these two P wells into a single P well in order to reduce the chipsize.

FIG. 8 depicts another embodiment in which devices 832, 833, 834 and 835correspond to devices 725, 726, 727, and 728 respectively in FIG. 7. Themajor difference between FIG. 7 and FIG. 8 is the implementation of thediode connected bipolar transistor. The diode connected bipolartransistor 832 in FIG. 8 has a Schottky base emitter junction while thecorresponding device 725 in FIG. 7 is having a normal base emitterjunction. An additional masking step is required to create the N−junction inside P well 803, which can have a deeper or shallowerjunction depth as compared with the N+ junctions. Interconnecting metalcontact via the barrier metal silicide 809 for connecting to the N−region inside the P well 803 is used to form the Schottky junction. Itis optional for the interconnecting metal to make contact to othersemiconductor regions direct, or via the barrier metal silicide (810,811, 814, 815, 816, 817, 818, 819, 821, 822, 824, 825, 826, 828, 829,831 and 836). Making connection for other regions via barrier metalsilicide has the possibility to save 1 masking step. Since P well 803and P well 804 are at the same potential (electrically connected), it ispreferred to merge these two P wells into a single P well in order toreduce the chip size.

Another embodiment is to change the diode connected transistor's baseemitter junction in FIG. 8 to a bulk silicon P+ junction. The actualequivalent circuit is the same as for FIG. 7. Cross section of such amonolithic device is illustrated in FIG. 9. Options applicable to FIG. 7are applicable to FIG. 9 in general.

Since the wells for the collector of the diode connected bipolar deviceas well as the base region of the Darlington device are of relativelyhigh doping concentration, the process control for forming a lightlydoped inversed region inside the diode connected bipolar device'scollector well is very tight. To alleviate the tight processing controlrequirements, FIG. 10 illustrates a cross section of device structure upto the forming the base region of the diode connected bipolar device.Further structures to complete the cross section (for either normalbipolar or Schottky bipolar) are similar to those shown in FIG. 8 andFIG. 9. In FIG. 10, the collector region 1005 for the diode connectedbipolar is having much lower dopant concentration as compared with Pwell region 1003 and 1004 that shield off region 1005 from high voltage.Hence, a lightly doped base region 1006 can be fabricated without tightprocessing control. P well 1003 together with 1004, and the high voltagecollector region 1002 will have pinch off below region 1005 during thetime when region 1001 is at high voltage. This ensures breakdown willnot occur at region 1005. Such diode connected bipolar structures can beused to replace the equivalent parts in FIG. 8 and FIG. 9.

FIG. 11 is the circuit diagram for an embodiment of the invented threepin high voltage hybrid MOSFET/bipolar power switching device with fastturn off time. Basically, this is the replacing of the first bipolartransistor of the circuit in FIG. 4 by a MOSFET such that the circuit isIGBT in nature. Similar to diode 403, diode 1103 provides the baserelaxation path during the turn off of the power switching device toensure fast switching off time. Again, a Schottky diode is preferredwhile a normal diode can function.

The three discrete semiconductor chips forming the invented high voltagehybrid MOSFET/bipolar power switching device can be packaged into asingle three pin IC. MOSFET and bipolar transistor used are having thebackside substrate as the drain and collector terminals respectivelywhile other terminals are at the front side with bonding pads. Diodehaving cathode as substrate and anode pad at front side is used. TheMOSFET and the bipolar transistor are die attached to the main die padusing conductive die attach epoxy. The main die pad and the collectorpin of the package are electrically connected. The diode is conductivedie attached to the base pin. Appropriate bonding connects the threeindividual discrete semiconductor chips into the circuit as shown inFIG. 11. Further steps such as plastic moulding, etc., to complete thepackaging are then carried out to complete the three pin packaging. FIG.12 illustrates the bonding diagram for inter-connecting the discretedevices into a single three pin package.

The three discrete devices forming the invented high voltage hybridMOSFET/bipolar power switching device can be fabricated as a monolithicintegrated circuit (IC). Use of high voltage SOI process is an obviousembodiment. Other possible embodiments are discussed in subsequentparagraphs.

The major difficulty in integrating the three discrete devices formingthe invented high voltage hybrid MOSFET/bipolar power switching deviceinto a monolithic IC using high voltage planer, super-junction, orsemi-super-junction processes is the isolation of the diode from thesubstrate. A simple diode using a base well as anode and the emitterelectrode inside the base well as cathode will not function due to theturn on of the vertical high voltage bipolar transistor having thesubstrate acting as the collector in the same way as for the verticalhigh voltage bipolar transistor. Similar to the high voltage Darlingtonpower switching device, a diode connected bipolar is used to providemeans to avoid the turn on of the parasitic transistor in the dioderegion.

FIG. 13 illustrates a possible cross section of a monolithic deviceintegrating the three devices, namely a high voltage MOSFET, a highvoltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device using high voltage planerprocess. The N− substrate 1302 serves as the drain and collector for thehigh voltage MOSFET 1327 and the high voltage bipolar transistor 1328respectively. It is connected to the collector terminal of the switchingdevice via the N+ backside 1301. P well 1305 serves as the base regionwhile N+ electrodes 1316, 1318, 1321, and 1323 serve as the emitterelectrodes for high voltage bipolar transistor 1328. P+ electrodes 1315,1317, 1319, 1320, 1322, and 1324 are optional electrodes for makingmetal contact to the base region 1305 of the high voltage bipolartransistor. P well 1304 serves as the body region while N+ electrodes1311 and 1313 serve as the source electrode, and the poly silicon 1310and 1314 having thin oxide over channel region and thick oxide overfield region serve as gate electrodes for the high voltage MOSFET 1327.P+ electrode 1312 is the optional electrode for making metal contact tothe body region 1304 of the high voltage MOSFET 1327. P well 1303 is thecollector for the diode connected bipolar 1325. N+ electrode 1307 is thebase electrode inside P well 1303 while P+ electrode 1308 serves as theemitter electrode inside base region 1307. Emitter 1308 serves as theanode of the diode while base 1307 and collector 1303 are connectedtogether by metal serve as the cathode of the diode. The main substrate1302, P well 1303 and N+ electrode 1307 form a parasitic bipolar 1326 atthe location while where the diode connected bipolar 1325 is located.Since the base emitter junction (1303 and 1307) of device 1326 is metalconnected as required by the diode connected bipolar 1325, the turn onof the parasitic bipolar 1326 is prevented. The source and body of thehigh voltage MOSFET 1327 is connected to the base of the high voltagebipolar transistor 1328, as well as to the anode of the diode connectedbipolar 1325. The gate of the high voltage MOSFET 1327 is connected tothe cathode of the diode connected bipolar 1325, and is also serving asthe gate terminal of the switching device. The emitter terminal of thehigh voltage bipolar transistor 1328 serves as the emitter terminal ofthe switching device. P+ electrodes 1306, 1309, 1312, 1315, 1317, 1319,1320, 1322, and 1324 are optional connecting electrodes for making metalcontact to the P well 1303, 1304, and 1305. Optionally, instead ofconnecting the body of the high voltage MOSFET to its own sourceelectrode, it is also possible to connect the body to the emitter of thehigh voltage bipolar 1328, although the former connection is preferred.If the body of the high voltage MOSFET 1327 is connected to its ownsource, since it is electrically having the same potential as the baseof the high voltage bipolar transistor 1328, P well 1304 and P well 1305can then be merged as a single well to save chip area.

FIG. 14 illustrates another possible cross section of a monolithicdevice integrating the three devices, namely a high voltage MOSFET, ahigh voltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltage planerprocess. The substrate 1402 serves as the drain and collector for thehigh voltage MOSFET 1437 and the high voltage bipolar transistor 1438respectively. It is connected to the collector terminal of the switchingdevice via the N+ backside 1401. P well 1405 serves as the base regionwhile N+ electrodes 1421, 1422, 1423, and 1424 serve as the emitterelectrodes for high voltage bipolar transistor 1438. P well 1404 servesas the body region while N+ electrodes 1412 and 1413 serve as the sourceelectrodes, and the poly-silicon electrodes 1415 and 1419 having thinoxide over channel region and thick oxide over field region serve asgate electrodes for the high voltage MOSFET 1437. P well 1403 is thecollector for the diode connected bipolar 1435. N− electrode 1407 is thebase electrode inside P well 1403 while the barrier metal silicideelectrode 1410 serves as the emitter electrode inside base region 1407(N− electrode 1407 and barrier metal silicide 1410 form the Schottkybase emitter junction). Connection to the base region 1407 is made viaN+ electrodes 1406 and 1408. Emitter 1410 serves as the anode of thediode while base 1407 and collector 1403 are connected together serve asthe cathode of the diode. Barrier metal silicide electrodes 1409, 1411,1414, 1416, 1417, 1418, 1420, 1425, 1426, 1427, 1428, 1429, 1430, 1431,1432, 1433, and 1434 are preferred optional electrodes for making metalcontacts to the semiconductor electrodes other than the emitterelectrode of the diode connected bipolar 1435.

Direct metal connections to these electrodes are possible but the formercase is preferred due to the possibility to share the same masking stepfor metal with the barrier metal silicide. The main N− substrate 1402, Pwell 1403 and N− electrode 1407 form a parasitic bipolar 1436 at thelocation while where the diode connected bipolar 1435 is located. Sincethe base emitter junction (1403 and 1407) of device 1436 is shorted asrequired by the diode connected bipolar 1435, the turn on of theparasitic bipolar 1436 is prevented. The source and body of the highvoltage MOSFET 1437 is connected to base of the high voltage bipolartransistor 1438, as well as to the anode of the diode connected bipolar1435. The gate of the high voltage MOSFET 1437 is connected to thecathode of the diode connected bipolar 1435, and is also serving as thegate terminal of the switching device. The emitter terminal of the highvoltage bipolar transistor 1438 serves as the emitter terminal of theswitching device. Optionally, instead of connecting the body of the highvoltage MOSFET 1437 to its own source electrode, it is also possible toconnect the body to the emitter of the high voltage bipolar 1438,although the former connection is preferred. If the body of the highvoltage MOSFET 1437 is connected to its own source, since it iselectrically having the same potential as the base of the high voltagebipolar transistor 1438, P well 1404 and P well 1305 can then be mergedas a single well to save chip area.

FIG. 15 illustrates another possible cross section of a monolithicdevice integrating the three devices, namely a high voltage MOSFET, ahigh voltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltage planerprocess. The substrate 1502 serves as the drain and collector for thehigh voltage MOSFET 1529 and the high voltage bipolar transistor 1530respectively. It is connected to the collector terminal of the switchingdevice via the N+ backside 1501. P well 1505 serves as the base regionwhile N+ electrodes 1518, 1520, 1523, and 1525 serve as the emitterelectrodes for high voltage bipolar transistor 1530. P well 1504 servesas the body region while N+ electrodes 1512 and 1514 serve as the sourceelectrodes, and the poly-silicon electrodes 1515 and 1516 having thinoxide over channel region and thick oxide over field region serve asgate electrodes for the high voltage MOSFET 1529. P well 1503 is thecollector for the diode connected bipolar 1527. N− electrode 1508 is thebase electrode inside P well 1503 while the P+ electrode 1511 serves asthe emitter electrode inside base region 1508. Connection to the baseregion 1508 is made via N+ electrodes 1507 and 1509. Emitter 1511 servesas the anode of the diode while base 1508 and collector 1503 areconnected together serve as the cathode of the diode. P+ electrodes1506, 1510, 1513, 1517, 1519, 1521, 1522, 1524, and 1526 are optionalelectrodes for making metal contacts to P wells 1503, 1504 and 1505while direct metal connections to these P wells is possible. The main N−substrate 1502, P well 1503 and N− electrode 1508 form a parasiticbipolar 1528 at the location where the diode connected bipolar 1527 islocated. Since the base emitter junction (1503 and 1508) of device 1527is metal connected as required by the diode connected bipolar 1527, theturn on of the parasitic bipolar 1528 is prevented. The source and bodyof the high voltage MOSFET 1529 is connected to base of the high voltagebipolar transistor 1530, as well as to the anode of the diode connectedbipolar 1527. The gate of the high voltage MOSFET 1529 is connected tothe cathode of the diode connected bipolar 1527, and is also serving asthe gate terminal of the switching device. The emitter terminal of thehigh voltage bipolar transistor 1530 serves as the emitter terminal ofthe switching device. Optionally, instead of connecting the body of thehigh voltage MOSFET 1529 to its own source electrode, it is alsopossible to connect the body of the high voltage MOSFET 1529 to theemitter of the high voltage bipolar 1530, although the former connectionis preferred. If the body of the high voltage MOSFET 1529 is connectedto its own source, since it is electrically having the same potential asthe base of the high voltage bipolar transistor 1530, P well 1504 and Pwell 1505 can then be merged as a single well to save chip area.

Since the wells for the collector of the diode connected bipolar device,the body of the high voltage MOSFET and the base region of the highvoltage bipolar transistor are of relatively high doping concentration,the process control for forming a lightly doped inversed region insidethe diode connected bipolar device's collector well is very tight. Theway to alleviate this problem is illustrated in FIG. 10 and had beendiscussed. Further structures to complete the cross section (for eithernormal bipolar or Schottky bipolar) are similar to those shown in FIG.14 and FIG. 15. Such diode connected bipolar structures can be used toreplace the equivalent parts in FIG. 14 and FIG. 15.

FIG. 16 illustrates another possible cross section of a monolithicdevice integrating the three devices, namely a high voltage MOSFET, ahigh voltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltagesuper-junction process. The N− substrate 1611 serves as the drain forthe high voltage MOSFET 1647 while N− substrate regions 1613 and 1614serve as the collector of the high voltage bipolar transistor 1648.These N− regions are connected to the collector terminal of theswitching device via the N+ backside 1601. Super-junction P+ columns1602, 1603, 1604, 1605, 1606, 1607 and 1608 are used together with N−substrate regions 1609, 1610, 1611, 1612, 1613 and 1614 to withstand thehigh breakdown voltage. P wells 1618 and 1619 serve as the base regionwhile N+ electrodes 1625, 1626, 1627, and 1628 serve as the emitterelectrodes for high voltage bipolar transistor 1648. P wells 1616 and1617 serve as the body regions while N+ electrodes 1623 and 1624 serveas the source electrodes, and the poly-silicon electrode 1633 havingthin oxide over channel region and thick oxide over field region serveas gate electrode for the high voltage MOSFET 1647. P well 1615 is thecollector for the diode connected bipolar 1645. N− electrode 1621 is thebase electrode inside P well 1615 while the barrier metal silicideelectrode 1630 serves as the emitter electrode inside base region 1621(N− well 1621 and barrier metal silicide 1630 form a Schottky baseemitter junction). Connection to the base region 1621 is made via N+electrodes 1620 and 1622. Emitter 1630 serves as the anode of the diodewhile base 1621 and collector 1615 are connected together serve as thecathode of the diode. Barrier metal silicide electrodes 1629, 1631,1632, 1634, 1635, 1636, 1637, 1638, 1639, 1640, 1641, 1642, 1643, and1644 are preferred optional barrier metal silicide electrodes for makingmetal contacts to the semiconductor electrodes other than the emitterelectrode of the diode connected bipolar 1645. Direct metal connectionsto these electrodes are possible but the former case is preferred due tothe possibility to share the same masking step for metal with thebarrier metal silicide. The N− substrate 1609, P well 1615 and N−electrode 1621 form a parasitic bipolar 1646 at the location where thediode connected bipolar 1645 is located. Since the base emitter junction(1615 and 1621) of device 1646 is shorted as required by the diodeconnected bipolar 1645, the turn on of the parasitic bipolar 1646 isprevented.

The source and body of the high voltage MOSFET 1647 are connected tobase of the high voltage bipolar transistor 1648, as well as to theanode of the diode connected bipolar 1645. The gate of the high voltageMOSFET 1647 is connected to the cathode of the diode connected bipolar1645, and is also serving as the gate terminal of the switching device.The emitter electrodes of the high voltage bipolar transistor 1648 serveas the emitter terminal of the switching device. Optionally, instead ofconnecting the body of the high voltage MOSFET 1647 to its own sourceelectrode, it is also possible to connect the body to the emitter of thehigh voltage bipolar 1648, although the former connection is preferred.If the body of the high voltage MOSFET 1647 is connected to its ownsource, since it is electrically having the same potential as the baseof the high voltage bipolar transistor 1648, P wells 1617, 1618 and 1619can then be merged as a single well to save chip area. Hence,super-junction columns 1605 and 1606 can be merged to eliminate the N−region 1612 for isolation purpose between them.

FIG. 17 illustrates the cross section of another possible monolithicdevice integrating the 3 devices, namely a high voltage MOSFET, a highvoltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltagesuper-junction process. The N− substrate 1711 serves as the drain forthe high voltage MOSFET 1739. N− substrate regions 1713 and 1714 serveas base for the high voltage bipolar transistor 1740. These N− regionsare connected to the collector terminal of the switching device via theN+ backside 1701. Super-junction P+ columns 1702, 1703, 1704, 1705,1706, 1707 and 1708 are used together with N− substrate regions towithstand the high breakdown voltage. P wells 1718 and 1719 serve as thebase region while N+ electrodes 1725, 1726, 1727, and 1728 serve as theemitter electrodes for high voltage bipolar transistor 1740. P wells1716 and 1717 serve as the body regions while N+ electrodes 1723 and1724 serve as the source electrodes, and the poly-silicon electrode 1736having thin oxide over channel region and thick oxide over field regionserves as gate electrode for the high voltage MOSFET 1739. P well 1715is the collector for the diode connected bipolar 1737. N− electrode 1721is the base electrode inside P well 1715 while the P+ electrode 1729serves as the emitter electrode inside base region 1721. Connection tothe base region 1721 is made via N+ electrodes 1720 and 1722. Emitter1729 serves as the anode of the diode while base 1721 and collector 1715are connected together to serve as the cathode of the diode. The N−substrate 1709, P well 1715 and N− electrode 1721 form a parasiticbipolar 1738 at the location where the diode connected bipolar 1737 islocated. Since the base emitter junction (1715 and 1721) of device 1738is metal connected as required by the diode connected bipolar 1737, theturn on of the parasitic bipolar 1738 is prevented. P+ electrodes 1730,1731, 1732, 1733, 1734, and 1735 are optional electrodes for makingmetal contacts to P wells 1718 and 1719 while direct metal connectionsto these P wells is possible. The source and body of the high voltageMOSFET 1739 are connected to base of the high voltage bipolar transistor1740, as well as to the anode of the diode connected bipolar 1737. Thegate of the high voltage MOSFET 1739 is connected to the cathode of thediode connected bipolar 1737, and is also serving as the gate terminalof the switching device. The emitter electrodes of the high voltagebipolar transistor 1740 serve as the emitter terminal of the switchingdevice. Optionally, instead of connecting the body of the high voltageMOSFET 1739 to its own source electrode, it is also possible to connectthe body of the high voltage MOSFET 1739 to the emitter of the highvoltage bipolar 1740, although the former connection is preferred. Ifthe body of the high voltage MOSFET 1739 is connected to its own source,since it is electrically having the same potential as the base of thehigh voltage bipolar transistor 1740, P wells 1717, 1718 and 1719 canthen be merged as a single well to save chip area. Hence, super-junctioncolumns 1705 and 1706 can be merged to eliminate the N− region 1712 forisolation purpose between them.

Since the wells for the collector of the diode connected bipolar device,the body of the high voltage MOSFET and the base region of the highvoltage bipolar transistor are of relatively high doping concentration,the process control for forming a lightly doped inversed region insidethe diode connected bipolar device's collector well is very tight. Theway to alleviate this problem is illustrated in FIG. 10 and had beendiscussed. Further structures to complete the cross section (for eithernormal bipolar or Schottky bipolar) are similar to those shown in FIG.16 and FIG. 17. Such diode connected bipolar structures can be used toreplace the equivalent parts in FIG. 16 and FIG. 17.

FIG. 18 illustrates another possible cross section of a monolithicdevice integrating the three devices, namely a high voltage MOSFET, ahigh voltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltagesemi-super-junction process. The N− substrate 1802 serves as the drainfor the high voltage MOSFET 1842 and the collector for the high voltagebipolar transistor 1843. The N− substrate 1802 is connected to thecollector terminal of the switching device via the N+ backside 1801.Semi-super-junction P+ columns 1803, 1804, 1805, 1806, 1807, 1808 and1809 are used together with N− substrate 1802 to withstand the highbreakdown voltage. P wells 1813 and 1814 serve as the base regions whileN+ electrodes 1820, 1821, 1822, and 1823 serve as the emitter electrodesfor high voltage bipolar transistor 1843. P wells 1811 and 1812 serve asthe body regions while N+ electrodes 1818 and 1819 serve as the sourceelectrodes, and the poly-silicon electrode 1828 having thin oxide overchannel region and thick oxide over field region serve as gate electrodefor the high voltage MOSFET 1842. P well 1810 is the collector for thediode connected bipolar 1840. N− electrode 1816 is the base electrodeinside P well 1810 while the barrier metal silicide electrode 1825serves as the emitter electrode inside base region 1816 (N− well 1816and barrier metal silicide 1825 form a Schottky base emitter junction).Connection to the base region 1816 is made via N+ electrodes 1815 and1817. Emitter 1825 serves as the anode of the diode while base 1816 andcollector 1810 are connected together serve as the cathode of the diode.Barrier metal silicide electrodes 1824, 1826, 1827, 1829, 1830, 1831,1832, 1833, 1834, 1835, 1836, 1837, 1838, and 1839 are preferredoptional barrier metal silicide electrodes for making metal contacts tothe semiconductor electrodes other than the emitter electrode of thediode connected bipolar 1840. Direct metal connections to theseelectrodes are possible but the former case is preferred due to thepossibility to share the same masking step for metal with the barriermetal silicide. The N− substrate 1802, P well 1810 and N− electrode 1816form a parasitic bipolar 1841 at the location where the diode connectedbipolar 1840 is located. Since the base emitter junction (1810 and 1816)of device 1841 is shorted as required by the diode connected bipolar1840, the turn on of the parasitic bipolar 1841 is prevented. The sourceand body of the high voltage MOSFET 1842 are connected to base of thehigh voltage bipolar transistor 1843, as well as to the anode of thediode connected bipolar 1840. The gate of the high voltage MOSFET 1842is connected to the cathode of the diode connected bipolar 1840, and isalso serving as the gate terminal of the switching device. The emitterelectrodes of the high voltage bipolar transistor 1843 serve as theemitter terminal of the switching device. Optionally, instead ofconnecting the body of the high voltage MOSFET 1842 to its own sourceelectrode, it is also possible to connect the body to the emitter of thehigh voltage bipolar 1843, although the former connection is preferred.If the body of the high voltage MOSFET 1842 is connected to its ownsource, since it is electrically having the same potential as the baseof the high voltage bipolar transistor 1843, P wells 1812, 1813 and 1814can then be merged as a single well to save chip area. Hence,super-junction columns 1806 and 1807 can be merged to eliminate the N−region for isolation purpose between them.

FIG. 19 illustrates the cross section of another possible monolithicdevice integrating the 3 devices, namely a high voltage MOSFET, a highvoltage bipolar transistor, and a diode, to form the invented highvoltage hybrid MOSFET/bipolar switching device by high voltagesemi-super-junction process. The N− substrate 1902 serves as the drainfor the high voltage MOSFET 1934 and the collector for the high voltagebipolar transistor 1935. The N− substrate 1902 is connected to thecollector terminal of the switching device via the N+ backside 1901.Semi-super-junction P+ columns 1903, 1904, 1905, 1906, 1907, 1908 and1909 are used together with N− substrate 1902 to withstand the highbreakdown voltage.

P wells 1913 and 1914 serve as the base regions while N+ electrodes1920, 1921, 1922, and 1923 serve as the emitter electrodes for highvoltage bipolar transistor 1935. P wells 1911 and 1912 serve as the bodyregions while N+ electrodes 1918 and 1919 serve as the sourceelectrodes, and the poly-silicon electrode 1925 having thin oxide overchannel region and thick oxide over field region serves as gateelectrode for the high voltage MOSFET 1934. P well 1910 is the collectorfor the diode connected bipolar 1932. N− electrode 1916 is the baseelectrode inside P well 1910 while the P+ electrode 1924 serves as theemitter electrode inside base region 1916. Connection to the base region1916 is made via N+ electrodes 1915 and 1917. Emitter 1924 serves as theanode of the diode while base 1916 and collector 1910 are connectedtogether to serve as the cathode of the diode. The N− substrate 1902, Pwell 1910 and N− electrode 1916 form a parasitic bipolar 1933 at thelocation where the diode connected bipolar 1932 is located. Since thebase emitter junction (1910 and 1916) of device 1933 is metal connectedas required by the diode connected bipolar 1932, the turn on of theparasitic bipolar 1933 is prevented. P+ electrodes 1926, 1927, 1928,1929, 1930, and 1931 are optional electrodes for making metal contactsto P wells 1913 and 1914 while direct metal connections to these P wellsis possible. The source and body of the high voltage MOSFET 1934 areconnected to base of the high voltage bipolar transistor 1935, as wellas to the anode of the diode connected bipolar 1932. The gate of thehigh voltage MOSFET 1934 is connected to the cathode of the diodeconnected bipolar 1932, and is also serving as the gate terminal of theswitching device.

The emitter electrodes of the high voltage bipolar transistor 1935 serveas the emitter terminal of the switching device. Optionally, instead ofconnecting the body of the high voltage MOSFET 1934 to its own sourceelectrode, it is also possible to connect the body of the high voltageMOSFET 1934 to the emitter of the high voltage bipolar 1935, althoughthe former connection is preferred. If the body of the high voltageMOSFET 1934 is connected to its own source, since it is electricallyhaving the same potential as the base of the high voltage bipolartransistor 1935, P wells 1912, 1913 and 1914 can then be merged as asingle well to save chip area. Hence, semi-super-junction columns 1906and 1907 can be merged to eliminate the N− region between them.

Since the wells for the collector of the diode connected bipolar device,the body of the high voltage MOSFET and the base region of the highvoltage bipolar transistor are of relatively high doping concentration,the process control for forming a lightly doped inversed region insidethe diode connected bipolar device's collector well is very tight. Theway to alleviate this problem is illustrated in FIG. 10 and had beendiscussed. Further structures to complete the cross section (for eithernormal bipolar or Schottky bipolar) are similar to those shown in FIG.18 and FIG. 19. Such diode connected bipolar structures can be used toreplace the equivalent parts in FIG. 18 and FIG. 19.

1. A method of fabricating a three terminal high voltage Darlingtonbipolar power switching device having a connector terminal, a baseterminal with a base pin, and an emitter terminal with an emitter pinand including the steps of: conductive die attaching first and secondhigh voltage bipolar transistors each having a substrate as a collectorterminal to a main die pad of a three pin power device package in whichthe main die pad is also electrically connected to the collectorterminal of the switching device; conductive die attaching a diodehaving a cathode and an anode with the cathode as a substrate to thebase bonding pin of the base terminal of the three pin power devicepackage; bonding the base of the first high voltage bipolar transistorto the base terminal of the three pin power device package; inter-chipbonding of the emitter of the first high voltage bipolar transistor tothe base of the second high voltage bipolar transistor; bonding of theemitter of the first high voltage bipolar transistor and/or the base ofthe second high voltage bipolar transistor to the anode of the diode;bonding of the emitter of the second high voltage bipolar transistor tothe emitter pin of the three pin power package; and subsequent standardmoulding and follow on process to complete a device packaging.
 2. Themethod of claim 1, wherein the diode is a Schottky diode.
 3. A method offabricating a three terminal high voltage Darlington bipolar powerswitching device having a connector terminal, a base terminal having abase bonding pin and an emitter terminal with an emitter pin includingthe steps of: conductive die attaching a single semiconductor chip highvoltage Darlington bipolar transistor having a collector, a first base,an inner base, and an emitter, with a substrate as the collectorterminal, to a main die pad of a three pin power device package in whichthe main die pad is also electrically connected to the collectorterminal of the switching device; conductive die attaching a diodehaving a cathode and an anode with the cathode as a substrate to thebase bonding pin of the base terminal of the three pin power devicepackage; bonding the first base of the high voltage Darlington bipolartransistor to the base terminal of the three pin power device package;bonding the base of the high voltage Darlington bipolar transistor tothe anode of the diode; bonding the emitter of the high voltageDarlington bipolar transistor to the emitter pin of the three pin powerpackage; and subsequent standard moulding and follow on process tocomplete a device packaging.
 4. The method of claim 3, wherein the diodeis a Schottky diode.
 5. A method of fabricating a three terminal highvoltage hybrid MOSFET/bipolar transistor power switching device having acollector terminal, a gate bonding terminal with a gate bonding pin andan emitter with an emitter pin, including the steps of: conductive dieattaching a high voltage MOSFET and a high voltage bipolar transistorhaving a substrate as a drain and a collector terminal respectively, toa main die pad of a three terminal power device, which serves as thecollector terminal for the power switching device; conductive dieattaching a diode having a cathode and an anode with the cathode as asubstrate to the gate bonding pin of the gate terminal of the threeterminal power device; bonding a gate of the high voltage MOSFET to thegate terminal of the three terminal power device package; inter-chipbonding of a source of the high voltage MOSFET to a base of the highvoltage bipolar transistor; bonding of the source of the high voltageMOSFET and/or a base of the high voltage bipolar transistor to the anodeof the diode; bonding of an emitter of the high voltage bipolartransistor to the emitter pin of the three pin power; and subsequentstandard moulding and follow on process to complete the device.
 6. Themethod of claim 5, wherein the diode is a Schottky diode.
 7. Amonolithic three terminal high voltage hybrid bipolar MOSFET/bipolarpower switching semiconductor integrated circuit having a collectorterminal, a gate terminal and an emitter terminal fabricated by a highvoltage planer process including: a high voltage MOSFET having a body, agate and a high voltage bipolar transistor, with a substrate having adopant type as a drain and a collector respectively such that thesubstrate serves as the collector terminal for the power switchingintegrated circuit via high doping concentration region of the same typeat a back side; two semiconductor well regions with an opposite dopanttype to the substrate serving as a body and a base region for the highvoltage MOSFET and high voltage bipolar transistor, respectively;semiconductor electrodes of the same dopant type as the substrate withhigh doping density inside the body and base regions serving as a sourceand an emitter for the high voltage MOSFET and high voltage bipolartransistors, respectively; poly-silicon thin oxide gate electrodesoverlapping the body and the substrate regions serving as the gate forthe MOSFET; wherein: the gate of the high voltage MOSFET serves as thegate terminal for the power switching integrated circuit; source of thehigh voltage MOSFET connecting to the base of the high voltage bipolartransistor; the body of the high voltage MOSFET connecting either to thesource of the high voltage MOSFET, or as an alternative, to an emitterof the high voltage bipolar transistor; the emitter of the high voltagebipolar transistor serving as an emitter terminal for the powerswitching integrated circuit; and a diode having an anode and a cathodewith the anode connected to the base of the high voltage bipolartransistor and the cathode connected to the gate terminal of the powerswitching integrated circuit; wherein: the diode is a diode connectedbipolar transistor with the following: a collector with a dopant typeopposite to the main substrate as a well on the high voltage collectorsubstrate of the high voltage power switching integrated circuit similarto the body of the high voltage MOSFET, or the base of the high voltagebipolar transistor; a base inside the collector well with a dopant typeopposite from that of the collector well with interconnections to otherparts via electrodes similar to the emitter of the high voltage bipolartransistor, or the source of the high voltage MOSFET; an emitter, eitheras semiconductor of the same type as the collector at much higher dopingdensity, or as barrier metal silicide; and the base and collector havingterminals which are connected and serve as the cathode while the emitterserves as the anode of the diode.
 8. The integrated circuit of claim 7comprising a mask for fabricating the wells for the body and baseregions of the high voltage MOSFET and high voltage bipolar transistor,wherein the collector well of the diode connected bipolar shares themask for fabricating the wells for the body and base regions of the highvoltage MOSFET and high voltage bipolar transistor, or as a separateregion fabricated by additional masking.
 9. The integrated circuit ofclaim 7, wherein the collector well of the diode connected bipolar hashigh doping density regions guarding a low doping density region of thesame type with a junction depth less than the high doping region whereinthe high doping regions are used for withstanding a high breakdownvoltage as well as connecting a low doping density collector well formaking connections, the low doping density region serving as an actualcollector well inside which the base and emitter of the diode connectedbipolar transmitter are formed.
 10. The integrated circuit of claim 7,wherein the wells for the body of the high voltage MOSFET and the baseof the high voltage bipolar transistor are merged for the case in whichthe body of the MOSFET is electrically connected to the base of the highvoltage bipolar transistor.
 11. The integrated circuit of claim 7,wherein the diode is a Schottky diode having an anode and connections tosemiconductor regions other than the Schottky diode anode are made viabarrier metal silicide.
 12. The integrated circuit of claim 7, whereinconnections to base region of the high voltage bipolar transistor andthe body region of the high voltage MOSFET, and the collector region ofthe diode connected bipolar transistor using a normal base emitterjunction are made via a same kind of semiconductor electrode for theanode of the diode.
 13. A monolithic three terminal high voltage hybridbipolar MOSFET/bipolar power switching semiconductor integrated circuithaving a gate terminal, an emitter terminal and a collector substratefabricated by high voltage super-junction process including: a highvoltage MOSFET having a drain and a high voltage bipolar transistorhaving a collector, a base and an emitter with a substrate as the drainand collector respectively such that the substrate has a dopant type andserves as a collector terminal for the power switching integratedcircuit via a high doping density region of the same type at a backside; semiconductor well regions with an opposite dopant type to thesubstrate serving as a body and base regions for the high voltage MOSFETand high voltage bipolar transistor, respectively, with high dopingconcentration super-junction columns of opposite type of dopant as themain substrate for withstanding a high breakdown voltage; semiconductorelectrodes of the same dopant type as the substrate with high dopingdensity inside the body and base regions serving as the source and anemitter for the high voltage MOSFET and high voltage bipolar transistorrespectively; poly-silicon thin oxide gate electrodes overlapping thebody and the substrate regions serving as a gate for the MOSFET;wherein: the gate of the high voltage MOSFET serves as a gate terminalfor the power switching integrated circuit; a source terminal of thehigh voltage MOSFET connecting to the base of the high voltage bipolartransistor; the body of the high voltage MOSFET connects to the sourceof the high voltage MOSFET, to the emitter of the high voltage bipolartransistor; the emitter of the high voltage bipolar transistor serves asan emitter terminal for the power switching integrated circuit; and adiode having an anode and a cathode with the anode connected to the baseof the high voltage bipolar transistor and the cathode connected to thegate terminal of the power switching integrated circuit; wherein thediode is a diode connected bipolar transistor with the following: acollector with dopant type opposite to the main substrate as a well onthe high voltage collector substrate of the high voltage power switchingintegrated circuit similar to the body of the high voltage MOSFET, orthe base of the high voltage bipolar transistor, with high dopingconcentration super-junction columns of opposite type of dopant of thesubstrate guarding the collector region for withstanding the highbreakdown voltage; a base inside the collector well with a dopant typeopposite from that of the collector well with interconnections to otherparts via electrodes similar to the emitter regions of the high voltagebipolar transistor, or the source of the high voltage MOSFET; anemitter, either as semiconductor of the same type as the collector atmuch higher doping density, or as a barrier metal silicide; and the baseand collector having terminals which are connected and serve as thecathode while the emitter serves as the anode of the diode.
 14. Theintegrated circuit of claim 13 comprising a mask for fabricating thewells for the body and base regions of the high voltage MOSFET and highvoltage bipolar transistor, wherein the collector well for the diodeconnected bipolar shares the mask for fabricating the wells for the bodyand base regions of the high voltage MOSFET and high voltage bipolartransistors, or as a separate region fabricated by additional masking.15. The integrated circuit of claim 13, wherein the collector well forthe diode connected bipolar has high doping density regions guarding alow doping density region of the same type with a junction depth lessthan the high doping region, wherein the high doping regions are usedfor withstanding the high breakdown voltage as well as connecting thelow doping density collector well for making connections, and the lowdoping density region is serving as the actual collector well insidewhich the base and emitter of the diode connected bipolar device areformed.
 16. The integrated circuit of claim 13, wherein the body of thehigh voltage MOSFET is electrically connected to the base of the highvoltage bipolar transistor, and the wells for the body of the highvoltage MOSFET and the base of the high voltage bipolar transistor aremerged.
 17. The integrated Circuit of claim 13, wherein isolation regionsuper-junction columns for the high voltage MOSFET and the high voltagebipolar transistor are merged and isolation regions between them areeliminated.
 18. The integrated circuit of claim 13, wherein the diode isa Schottky diode and connections to semiconductor regions other than theSchottky diode anode are made via barrier metal silicide.
 19. Theintegrated circuit of claim 13, wherein connections to base region ofthe high voltage bipolar transistor and the body region of the highvoltage MOSFET, and the collector region of the diode connected bipolardevice using normal base emitter junction are made via the same kind ofsemiconductor electrode for the anode of the diode.
 20. A monolithicthree terminal high voltage hybrid bipolar MOSFET/bipolar powerswitching semiconductor integrated circuit having a collector terminal,a gate terminal and an emitter terminal and fabricated by high voltagesemi-super-junction process comprising: a high voltage MOSFET having abody, a gate, a source and a drain and a high voltage bipolartransistor, having a base, a collector and an emitter, with a substrateas the drain and the collector, respectively, such that the substratehas a dopant type and serves as the collector terminal for the powerswitching integrated circuit via a high doping density region of thesame type at a back side; semiconductor well regions with an oppositedopant type to the substrate serving as the body and base regions forthe high voltage MOSFET and high voltage bipolar transistor,respectively, with high doping concentration semi-super-junction columnsof opposite type of dopant as a main substrate for withstanding a highbreakdown voltage; semiconductor electrodes of the same dopant type asthe substrate with high doping density inside the body and base regionsserving as the source and the emitter for the high voltage MOSFET andhigh voltage bipolar transistor, respectively; poly-silicon thin oxidegate electrodes overlapping the body and the substrate serving as thegate for the MOSFET; wherein: the gate of the high voltage MOSFET servesas the gate terminal for the power switching integrated circuit; thesource of the high voltage MOSFET connecting to the base of the highvoltage bipolar transistor; the body of the high voltage MOSFET connectsto the source of the high voltage MOSFET, or to the emitter of the highvoltage bipolar transistor; the emitter of the high voltage bipolartransistor serving as the emitter terminal for the power switchingintegrated circuit; and a diode having an anode and a cathode with theanode connected to the base of the high voltage bipolar transistor andthe cathode connected to the gate terminal of the power switchingintegrated circuit; wherein the diode is a diode connected bipolartransistor with the following: a collector having a region with a dopanttype opposite to the main substrate as a well on the high voltagecollector substrate of the high voltage power switching integratedcircuit similar to the body of the high voltage MOSFET, or the base ofthe high voltage bipolar transistor, with high doping concentrationsemi-super-junction columns of opposite type of dopant of the substrateguarding the collector region for withstanding the high breakdownvoltage; a base inside the collector well with dopant type opposite fromthat of the collector well with interconnections to other parts viaelectrodes similar to the emitter regions of the high voltage bipolartransistor, or the source of the high voltage MOSFET; an emitter, eitheras semiconductor of the same type as the collector at much higher dopingdensity, or as barrier metal silicide; and the base and collector havingterminals which are connected and serve as the cathode while the emitteris serving as the anode of the diode.
 21. The integrated circuit ofclaim 20 and comprising a mask for fabricating the wells for the bodyand base regions of the high voltage MOSFET and high voltage bipolartransistor, wherein the collector well of for the diode connectedbipolar shares the mask for fabricating the wells for the body and baseregions of the high voltage MOSFET and high voltage bipolar transistor,or as a separate region fabricated by additional masking.
 22. Theintegrated circuit of claim 20, wherein the collector well of the diodeconnected bipolar has high doping density regions guarding a low dopingdensity region of the same type with a junction depth less than the highdoping region wherein the high doping regions are used for withstandingthe high breakdown voltage as well as connecting the low doping densitycollector well for making the connection, the low doping density regionserving as the actual collector well inside which the base and emitterof the diode connected bipolar transistor are formed.
 23. The integratedcircuit of claim 20, wherein the wells for the body of the high voltageMOSFET and the base of the high voltage bipolar transistor are mergedfor the case in which the body of the high voltage MOSFET iselectrically connected to the base of the high voltage bipolartransistor.
 24. The integrated circuit of claim 23 wherein isolationregion semi-super-junction columns for the high voltage MOSFET and thehigh voltage bipolar transistor are merged and an isolation regionbetween them are eliminated.
 25. The integrated circuit of claim 20,wherein the diode is a Schottky diode and connections to semiconductorregions other than the Schottky diode anode are made via barrier metalsilicide.
 26. The integrated circuit of claim 20, wherein connections tothe base region of the high voltage bipolar transistor and the bodyregion of the high voltage MOSFET, and the collector region of the diodeconnected bipolar device using normal base emitter junction are made viathe same kind of semiconductor electrode for the anode of the diode.